This invention relates to a photochemical process for making a device with a three-dimensionally tapered point suitable for needles, staples and other pointed devices.
Numerous pointed devices, such as surgical needles, are typically prepared one at a time by a multistep, labor-intensive process from stainless steel wire. U.S. Pat. Nos. 4,587,202 and 4,777,096 (Borysko patents) disclose an alternative process for preparing surgical needles without requiring the high degree of manual labor associated with conventional processes. A metal sheet exhibiting the properties desired for a surgical needle is first coated on at least one surface with a light-sensitive photoresist, preferably on both the top and bottom surfaces thereof, and then the coated surfaces are exposed to light in the form of an image of a plurality of surgical needles where each needle is shaped with a square blunt end to compensate for lateral etching which occurs during a later etching step. The image of the needles is typically prepared by covering the coated metal sheet with a negative or photomask. The photomask contains a light-impenetrable mask shaped in the form of the surgical needles, so that when the sheet is exposed to light, an image of the needles is created on the coated surface corresponding to the shape of the light-impenetrable mask. The exposed photoresist is removed and unwanted metal not protected by the remaining photoresist is etched away in an etching solution. In the preferred process, the images of the surgical needles for the top and bottom surfaces of the metal sheet are mirror images of each other precisely superimposed. After removing the photoresist from the needles prepared, the needles can be electropolished, attached to sutures, and then sterilized for surgical applications. This process affords an alternative to the slow mechanical production of surgical needles one at a time, and reduces the manpower and therefore the overall cost of preparing such needles.
Unfortunately, the needles produced by the Borysko patents have points terminating with chisel-shaped tips which resist penetration and may tear tissue during surgical procedures. In view of this problem, it would be desirable to improve upon this process so that a symmetrical three-dimensionally tapered point having the ability to easily penetrate tissue or other material can be prepared by a photoetching process.